Apparatus for making multi layer capacitors

ABSTRACT

The ceramic layer of multi-layered ceramic capacitors is provided by pressure rolling powders into sheets or films. A machine used to roll the powder utilizes a feed control roll disposed between and in working relationship between a stationary back-up roll and an adjustable compression roll.

United States Patent [191 Fuller et al.

[451 Oct. 8, 1974 APPARATUS FOR MAKING MULTI LAYER CAPACITORS lnventors: Fred J. Fuller, Chicago; John G.

Kirschner, Northbrook; Richard A. Stark, Des Plaines, all of 111.

P. R. Mallory & Co. Inc., Indianapolis, Ind.

Filed: Oct. 30, 1972 Appl. No.: 302,029

[73] Assignee:

US. Cl 425/367, 425/335, 425/363, 425/456 Int. Cl. B29c 1-5/00 Field of Search 425/335, 367, 363, 115, 425/79, 223, 224, 456

References Cited UNITED STATES PATENTS 9/1918 Kearns 425/335 'PrimaryExaminer-Robert L. Spicer, Jr.

Attorney, Agent, or Firm-Charles W. Hoffmann; Robert F. Meyer ABSTRACT The ceramic layer of multi-layered ceramic capacitors is provided by pressure rolling powders into sheets or films. A machine used to roll .the powder utilizes a feed control r011 disposed between and in working relationship between a stationary :back-up roll and an adjustable compression roll.

60mm, v8 Drawing Figures am 81974 840,315 PATENTED saw 1 or 4 3 TERMIN ATI ON PATENTED DU 74 SHEEI 30? 4 APPARATUS FOR MAKING MULTI LAYER CAPACITORS This invention relates to multi-layered ceramic capacitors; and more particularly it relates to such 21 capacitor having powder rolled ceramic layers and to a means and method of providing such layers.

Multi-layered miniature capacitors are used extensively in hybrid integrated circuits and microminaturized printed circuits. Such capacitors provide higher capacitor values than those attained in monolithic integrated circuits. In order to meet its intended uses, such capacitors should enclose a high electrical capacitance within a small volume and it should also be capable of simple and inexpensive manufacture.

For the most part such capacitors have been made by a slip casting technique. While for the most part satisfactory, this technique is somewhat time consuming and expensive. In addition, capacitors made by the slip casting process sometimes has pinholes such that there was short circuiting and dielectric failure.

The present invention is concerned with the making of multi-layered ceramic capacitors and has as one of its objects the provision of a multi-layered ceramic capacitor having substantially no pinholes or voids in its structure. I

Another object of the invention is the provision of a multi-layered ceramic capacitor wherein the ceramic layers are formed by powder rolling techniques.

Still another object of the invention is the provision of a powder rolling machine. I

Yet another object of the invention is the provision of a powder rolling machine capable of rolling ceramic powders into a very fine film.

Another object of the invention is the provision of a powder rolling machine having a stationary backup roll and an adjustable compression roll with a drive and feed control roll disposed between the stationary and compression roll and in working relationship therewith.

These and other objects of the invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein:

FIG. 1 is an enlarged photograph of a partial section of a multi-layered ceramic capacitor;

FIG. 2 is a schematic showing a process step in forming multi-layered ceramic capacitors according to the invention;

FIG. 3 is a schematic showing another process step in forming the capacitors;

FIG. 4 is a front elevation of a powder'rolling machine; v FIG. 5 is a section taken along the line 55 FIG. 4;

FIG. 6 is a top view of a portion of the machine;

FIG. 7 is a transfer of FIG. 6; and

FIG. 8 is a perspective view of an element of the powder rolling machine.

Generally speaking, the present invention is directed to a multi-layered ceramic capacitor comprising a body containing a plurality of alternate layers of pressure rolled ceramic and metallic electrodes and outer termination layer portions electrically connecting alternate electrode layers.

The multi-layered ceramic capacitor is fabricated by passing powders of the ceramic through a rolling machine to compact the powder into a very thin sheet or film, printing metallic electrodes on the sheet in a pre-' determined pattern, pressure bonding a predetermined number of the sheets together, trimming, if necessary, the sheets to a predetermined size, and then applying termination layers portions to ends of the sheet to electrically connect alternate electrode layers.

A powder rolling machine particularly adaptable to rolling the ceramic powder into the required film, in general includes a stationary back up'roll, an adjustable compression roll, a drive and feed control roll disposed between the back-up and compression rolls and in working relationship therewith, and means supplying powder to a compacting area defined by the compression roll and the drive and feed control roll.

Referring now to the drawings, and in particular F IG. 1, there is shown a multi layered ceramic capacitor, which in general comprises a body 10 which is composed of ceramic layers 12 each separated by an inner electrode layer 14. The electrodes 14 extend substantially over-the interface between adjacent ceramic layers. The inner-electrode layers alternate in their extension to the oppositely opposedends of the ceramic layers and the alternate innerelectrode layers are electrically connected by outertermination or electrode layer portions .16 and l'8 thus providing alternate polarity electrodes oversubstantially all'of the ceramic layers therebetween.. The outer termination layer portions usually encase each end of the body as well as provide an electrode portion for attachment intoelectrical ciruitry. It should be understood that although three layers of ceramic and two'layers of electrodes are shown, the invention need not be so limited and that any number of desired layers may be used. v I

The ceramic materials which can be employed include one or more ceramic constituents, such as barium, calcium, lead and/or strontium titanatewi'th or without the addition of zirconates of the abovementioned and other metals and metallic oxides. These usually produce ceramics of. relatively high dielectric con= stant generally desirable for relatively high capacitance capacitors.

Metals which can be employed as electrodesand termination portions include metallic conductors and their alloys. Preferably such metals should not deleteriously react or alloy with the constituents, such as the metallic constituents, of the ceramic material. Typical metals include high temperature metals and alloys which have melting points at or above the sintering temperature of the ceramic material'such as refractory metals i.e., tungsten, molybdenum and the like, and alloys containing such, and the noble metals such as palladium, platinum, gold and silver and alloys containing such.

According to a feature of thepresent invention, the ceramic layers 12 are provided by pressure rolling ce-' ramic powders into a thin sheet of film. It hasbeen found that when the ceramic layers are so formed that there is'substantially no failure of the dielectric or short circuiting. It is believed that such improved properties of the capacitor are achieved by virtue of the powder rolled material being relatively dense with substantially no pinholes with a more uniform ceramic film;

Referring to FIGS. 2 and 3 there is shown schematically the process steps for forming the multi-layered capacitor of FIG. 1 using powder rolled ceramic for layers 12. Powders of a suitable ceramic are'fed to pressure rolls 20, 22 and 24 with the powder being rolled'primarily between rolls 20 and 24, roll 22 being a back-up roll. The rolled powder emanates from the rolls as a very thin sheet or film 26. The inner electrodes 14 are then printed on the film in a predetermined pattern through a suitable printing applicator means 28. The electrodes may be applied as a metallic paste or paint, for example. The sheets are then cut to a predetermined size and then, as shown in FIG. 3 are fed to a press means 32 to be bonded together to form a body 36 which is then trimmed to a predetermined size 38 through cutting means 39. As indicated, outer termination layer 16 and 18 (FIG. 1) are then applied to complete the body of FIG. 1. The application of the termination layers and electrical terminals for attachment into electrical circuits may be accomplished in a manner well known in the capacitor art and form no part of the present invention. For example, well known dipping techniques may be used.

Referring now toFIGS. 4-8, there is shown a machine particularly adaptable to rolling powders of ceramics, such as previously noted, into very fine sheets or films. In generaLthe fine film is achieved through a three roll machine wherein asmall center roll is used as the drive and feed roll with the powders being rolled between it and another larger roll. A third larger-roll 40 and 42 carried on a suitable base 44. A second pair of plates 46 and 48 are pivotally mounted on plates 40 and 42 through a pair of plates 50 coupled to a shaft 52, the shaft being rotatably mounted in plates 40 and 42. Rotatably journalled in plates 40 and 42 is a relatively large roll 54. A second large roll 56 is rotatably journalled in plates 46 and 48. Since roll 54 is carried by fixed plates 40 and 42 it is stationary as opposed to roll 56 which is movable, being carried by pivotally mounted plates 46 and 48.

A third center roll 58 of relatively smaller diameter is rotatably journalled in plates 40 and 42 and disposed in working relation between rolls 54 and 56. Roll 58 is disposed substantially on a line through the centers of rolls 54 and 56. As shown in the illustrative embodiment, roll 58 serves as a drive and feed control roll. However, it should be understood that the invention need not be so limited and that either of the other rolls may serve as the drive roll. Roll 58 is power driven through a suitable motor, the roll being coupled to the motor through pinion 60 which is fixedly carried by the roll, worm gear 62 which is fixedly carried on shaft 64, shaft 64 being rotated by the motor through chain drive 66 and suitable gear means disposed in housing 68. As shown, shaft 64 rotates in bearings 70 and 72. Rotation of roll 58 causes rotation of rolls 54'and 56; thus rolls 54 and 52 are driven by the-center roll. As viewed in FIG. 7, center roll 58 is driven clockwise to drive rolls -54 and 56 counter-clockwise and clockwise respec- From the screen 80, the powder is fed through a com partment 81 formed by side walls 82, 84, 85, and 87.

- As shown in FIG. 7, wall 82 limits the powder compartment area so as to direct the powder away from the face of roller 56 until the powder reaches an area between roller 58 and the roll 56. Or, more precisely, the powder is directed away from roll 56 until it reaches the bite between rolls 56 and 58. Thus, the center roll 58 is the feed roll. This aids in maintaining a fine feed control of the powder so that close tolerances can be achieved in rolling the powder to a very fine sheet or film, for example 0.001 to 0.004 inches.

There is a blade 102 engaging roll 58 to maintain the roll free of powder. The blade is carried on a support 104 which is carried by plates 40 and 42. Similarly, as indicated in FIG. 4, there are blades 106 and 108 carried by plates 40, 42 and 46, 48 respectively to clean rolls 54 and 56 respectively.

A pair of micrometer adjusting means 110 provides for pivoting of the plates 46 and 48, thus permitting roll 56 to be adjusted. Each micrometer adjusting means 110 includes a pairof nuts 112 and 114, one each carried by the plates 40, 42 and 46, 48, and bolt 116 engaging the nuts. There is a thread differential between the two nuts so that a mechanical advantage is achieved when plates 46, 48 are pivoted by turning handle 111.

Referring to FIG. 8,'another feature of the machine is shown, As shown roll 58-, blade 102 and its support frame 104, pinion 60, and support blocks 116, 118, and arefabricated as a single unit to provide a cartridge 115. Blocks 116 and 118 are adapted to be received by plates 40 and 42. Notches 41 of the blocks receive pro- In operation, powder is fed through screen 80 through compartment8l to the compacting. area 74. The powder will be rolled between rolls 56 and 58, roll 54 serving as a back up roll. Rolls 58 will serve as the drive roll driving rolls 56 and 58 through friction. Since there is substantially no powder reaching roll 56 until an area at the bite between rolls 54 and 56, roll 58 will determine the rate of feed for better and close tolerances. The powder passing between the rolls will be rolledinto a thin sheet or film.

What is claimedis:

1. A powder rolling machine comprising:

a. a'base, 4

. b. a first pair of spaced upstanding plates carried by said base,

c. a first roll rotatably carried by said first pairof plates, d. a second pair of spaced upstanding plates pivotally carried by said first pair of plates, 7

e. coupling means connecting said first and second pair of plates in a spaced predetermined position,

f. a second, roll rotatably carried by said second pair of plates in spaced relation to said. first roll,

compression rolls.

6 g. a cartridge carried by said first pair of plates, said a. a pair of spaced blocks adapted to engage said first cartridge including a rotatably mounted feed conpair of plates, V trol roll disposed betwe n n i rk g relation b. means rotatably journalling said feed control roll to said first and Second rolls, in said blocks, said feed control roll extending means pp y Powder to a cPmpacting area 5 through and beyond one of said blocks, and

fined by sald Second and Said feed comm! 0. means coupling said feed control roll to said means and i. means applying power driven rotation to said feed control roll. 2. A powder rolling machine according to claim 1 10 wherein said feed control roll is substantially smaller in diameter than said stationary backup and adjustable applying power driven rotation. v 5. A powder rolling machine according to claim 1 wherein said coupling means comprises a pair of miond pair of plates.

6. A powder rolling machine according to claim 1 A powder rolling machine according to claim 1 wherein said means applying power driven rotation wherein said coupling means comprises a pair of micomprlsesi crometer adjusting means coupling said first and seca motor carried y Said base, 0nd pair of plates. b. a drive shaft, and

4. A powder rolling machine according in claim 1 c. means coupling said motor to said drive shaft. wherein said cartridge comprises:

crometer adjusting means carried by said first and sec- 

1. A powder rolling machine comprising: a. a base, b. a first pair of spaced upstanding plates carried by said base, c. a first roll rotatably carried by said first pair of plates, d. a second pair of spaced upstanding plates pivotally carried by said first pair of plates, e. coupling means connecting said first and second pair of plates in a spaced predetermined position, f. a second roll rotatably carried by said second pair of plates in spaced relation to said first roll, g. a cartridge carried by said first pair of plates, said cartridge including a rotatably mounted feed control roll disposed between and in working relation to said first and second rolls, h. means supplying powder to a compacting area defined by said second roll and said feed control roll, and i. means applying power driven rotation to said feed control roll.
 2. A powder rolling machine according to claim 1 wherein said feed control roll is substantially smaller in diameter than said stationary backup and adjustable compression rolls.
 3. A powder rolling machine according to claim 1 wherein said coupling means comprises a pair of micrometer adjusting means coupling said first and second pair of plates.
 4. A powder rolling machine according in claim 1 wherein said cartridge comprises: a. a pair of spaced blocks adapted to engage said first pair of plates, b. means rotatably journalling said feed control roll in said blocks, said feed control roll extending through and beyond one of said blocks, and c. means coupling said feed control roll to said means applying power driven rotation.
 5. A powder rolling machine according to claim 1 wherein said coupling means comprises a pair of micrometer adjusting means carried by said first and second pair of plates.
 6. A powder rolling machine according to claim 1 wherein said means applying power Driven rotation comprises: a. a motor carried by said base, b. a drive shaft, and c. means coupling said motor to said drive shaft. 